The overall goal of this project is to define the role of cellular calcium homeostasis in the acute and chronic actions of alcohol and barbiturates. Intracellular levels of ionized calcium will be measured with fluorescent indicators. Intracellular sequestration and release of calcium will be determined using 45Ca. This sequestration is non-mitochondrial and dependent upon ATP, whereas the release of calcium is stimulated by inositol, 1,4,5-trisphosphate (IP3). These parameters will be measured in brain synaptosomes, hepatocytes and cultured pheochromocytoma (PC12) and hepatoma (H35) cells. Effects of acute, in vitro, exposure to ethanol and barbiturates, and chronic, in vivo and in vitro, exposure to these drugs will be studied. These experiments will seek to define the role of intracellular calcium in alcohol and sedative intoxication, tolerance and dependence. In addition, they will provide information about the suitability of cultured cells for investigating the cellular mechanisms responsible for these health problems.